Aggregation methods and systems for multi-user mimo or ofdma operation

ABSTRACT

In an example of multi-user wireless communications, an access point may send a downlink frame, including a first signaling field and a second signaling field, to multiple stations. The first and second signaling fields are located in a header of the downlink frame. The first signaling field indicates whether the downlink frame is associated with a multi-user (MU) multi-input multi-output (MIMO) transmission. The second signaling field includes an attribute of the MU-MIMO transmission or a non-MU-MIMO transmission. A resource unit of the downlink frame includes a MU-MIMO payload when the downlink frame is associated with the MU-MIMO transmission. A resource unit of the downlink frame includes a non-MU-MIMO payload when the downlink frame is associated with the non-MU-MIMO transmission. The stations may decode one or more portions of the downlink frame based on the attribute in the second signaling field. Other methods, apparatus, and computer-readable media are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of application Ser. No.15/991,889, filed on May 29, 2018, which is a continuation applicationof application Ser. No. 15/083,185, filed on Mar. 28, 2016, now U.S.Pat. No. 9,998,185, which claims the benefit of U.S. ProvisionalApplication No. 62/271,870, filed on Dec. 28, 2015, U.S. ProvisionalApplication No. 62/142,394, filed on Apr. 2, 2015, and U.S. ProvisionalApplication No. 62/139,574, filed on Mar. 27, 2015, the entirety of eachof which is incorporated herein by reference for all purposes.

TECHNICAL FIELD

The present description relates in general to wireless communicationsystems and methods, and more particularly to, for example, withoutlimitation, aggregation methods and systems for multi-user (MU)multiple-input/multiple-output (MIMO) or orthogonal frequency-divisionmultiple access (OFDMA) operation.

BACKGROUND

Wireless local area network (WLAN) devices are deployed in diverseenvironments. These environments are generally characterized by theexistence of access points and non-access point stations. Increasedinterference from neighboring devices gives rise to performancedegradation. Additionally, WLAN devices are increasingly required tosupport a variety of applications such as video, cloud access, andoffloading. In particular, video traffic is expected to be the dominanttype of traffic in many high efficiency WLAN deployments. With thereal-time requirements of some of these applications, WLAN users demandimproved performance in delivering their applications, includingimproved power consumption for battery-operated devices.

The description provided in the background section should not be assumedto be prior art merely because it is mentioned in or associated with thebackground section. The background section may include information thatdescribes one or more aspects of the subject technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processor in a wireless communication device.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processor in a wireless communication device.

FIG. 4 illustrates a schematic diagram of an example of a format of ahigh efficiency (HE) physical layer convergence procedure (PLCP)protocol data unit (HE PPDU) frame.

FIG. 5 illustrates a schematic diagram of an example of a downlink (DL)OFDMA PPDU transmission to a set of stations (STAs).

FIG. 6 illustrates a schematic diagram of an example of a DL OFDMA PPDUtransmission to a set of STAs.

FIG. 7 illustrates a schematic diagram of an example of a DL OFDMA PPDUtransmission to a set of STAs.

FIG. 8 illustrates a schematic diagram of an example of a sequence toindicate the presence and attributes of subsequent PLCP service dataunits (PSDU)s along with the PSDU attributes.

FIG. 9 illustrates an example of a DL OFDMA PPDU transmission to a setof STAs.

FIG. 10 illustrates a schematic diagram of an example of a sequence toindicate the presence and attributes of subsequent PSDUs along with thePSDU attributes.

FIG. 11 illustrates an example of a DL OFDMA PPDU transmission to a setof STAs.

FIG. 12 illustrates a schematic diagram of an example of a sequence toindicate the presence of sub-bands with several PSDU attributes.

FIGS. 13A and 13B illustrate schematic diagrams of examples ofdifferential encoding for length indication.

FIGS. 14A through 14C illustrate flow charts of examples of aggregationmethods for OFDMA operation.

In one or more implementations, not all of the depicted components ineach figure may be required, and one or more implementations may includeadditional components not shown in a figure. Variations in thearrangement and type of the components may be made without departingfrom the scope of the subject disclosure. Additional components,different components, or fewer components may be utilized within thescope of the subject disclosure.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious implementations and is not intended to represent the onlyimplementations in which the subject technology may be practiced. Asthose skilled in the art would realize, the described implementationsmay be modified in various different ways, all without departing fromthe scope of the present disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature and notrestrictive.

New multi-user (MU) transmissions, such as downlink (DL) orthogonalfrequency division multiple access (OFDMA) and DL MUmultiple-input/multiple-output (MIMO), provide new opportunities fornext-generation WiFi technology. For example, OFDMA is a technique thatcan be used in WiFi technology in order to enhance the aggregation ofmultiple payloads that are destined to multiple stations (STAs) withinthe same frame. Due to this and other advantages, OFDMA technique isbeing considered for next generation WLAN technologies, including802.11ax which is also referred to as high efficiency (HE) technology.

With OFDMA technique, there comes new opportunities and challenges thatshould be considered in the design of OFDMA signaling and procedures.Among the opportunities that are provided by OFDMA is the frequencyselectivity gain, where AP would allocate resources to each STA wherethose allocated resources offer highest frequency-gain for that STA.Using acknowledgement procedures, the AP can obtain the information thatis needed to harvest frequency selectivity gain for each STA in thesubsequent DL or uplink (UL) OFDMA frames.

One or more aspects of the present disclosure describe methods that canbe used between a pair of e.g., 802.11 nodes while they exchange framesin MU-MIMO or OFDMA format. In MU-MIMO or OFDMA transmission, thetransmitter node, commonly an AP in 802.11 use cases, sends an MU-MIMOor OFDMA frame to several other clients. One or more aspects of thepresent disclosure provide several aggregation methods for DL MU-MIMO orOFDMA transmission. In addition, one or more aspects of the presentdisclosure provide methods to indicate the length of each payload thatexists in a DL OFDMA physical layer convergence protocol (PLCP) protocoldata unit (PPDU).

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network 100. In the wireless communication network 100,such as a wireless local area network (WLAN), a basic service set (BSS)includes a plurality of wireless communication devices (e.g., WLANdevices). In one aspect, a BSS refers to a set of STAs that cancommunicate in synchronization, rather than a concept indicating aparticular area. In the example, the wireless communication network 100includes wireless communication devices 111-115, which may be referredto as stations (STAs).

Each of the wireless communication devices 111-115 may include a MAClayer and a physical (PHY) layer according to an IEEE 802.11 standard.In the example, at least one wireless communication device (e.g., device111) is an access point (AP). An AP may be referred to as an AP STA oran AP device. The other wireless communication devices (e.g., devices112-115) may be non-AP STAs. Alternatively, all of the wirelesscommunication devices 111-115 may be non-AP STAs in an Ad-hoc networkingenvironment.

An AP STA and a non-AP STA may be collectively called STAs. However, forsimplicity of description, in some aspects, only a non-AP STA may bereferred to as a STA. An AP may be, for example, a centralizedcontroller, a base station (BS), a node-B, a base transceiver system(BTS), a site controller, a network adapter, a network interface card(NIC), a router, or the like. An non-AP STA (e.g., a client deviceoperable by a user) may be, for example, a device with wirelesscommunication capability, a terminal, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal,a mobile subscriber unit, a laptop, a non-mobile computing device (e.g.,a desktop computer with wireless communication capability) or the like.In one or more aspects, a non-AP STA may act as an AP (e.g., a wirelesshotspot).

In one aspect, an AP is a functional entity for providing access to adistribution system, by way of a wireless medium, for an associated STA.For example, an AP may provide access to the internet for one or moreSTAs that are wirelessly and communicatively connected to the AP. InFIG. 1, wireless communications between non-AP STAs are made by way ofan AP. However, when a direct link is established between non-AP STAs,the STAs can communicate directly with each other (without using an AP).

In one or more implementations, OFDMA-based 802.11 technologies areutilized, and for the sake of brevity, a STA refers to a non-AP HE STA,and an AP refers to a HE AP. In one or more aspects, a STA may act as anAP.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device. The wireless communication device 200 includes abaseband processor 210, a radio frequency (RF) transceiver 220, anantenna unit 230, a memory 240, an input interface unit 250, an outputinterface unit 260, and a bus 270, or subsets and variations thereof.The wireless communication device 200 can be, or can be a part of, anyof the wireless communication devices 111-115.

In the example, the baseband processor 210 performs baseband signalprocessing, and includes a medium access control (MAC) processor 211 anda PHY processor 215. The memory 240 may store software (such as MACsoftware) including at least some functions of the MAC layer. The memorymay further store an operating system and applications.

In the illustration, the MAC processor 211 includes a MAC softwareprocessing unit 212 and a MAC hardware processing unit 213. The MACsoftware processing unit 212 executes the MAC software to implement somefunctions of the MAC layer, and the MAC hardware processing unit 213 mayimplement remaining functions of the MAC layer as hardware (MAChardware). However, the MAC processor 211 may vary in functionalitydepending on implementation. The PHY processor 215 includes atransmitting (TX) signal processing unit 280 and a receiving (RX) signalprocessing unit 290. The term TX may refer to transmitting, transmit,transmitted, transmitter or the like. The term RX may refer toreceiving, receive, received, receiver or the like.

The PHY processor 215 interfaces to the MAC processor 211 through, amongothers, transmit vector (TXVECTOR) and receive vector (RXVECTOR)parameters. In one or more aspects, the MAC processor 211 generates andprovides TXVECTOR parameters to the PHY processor 215 to supplyper-packet transmit parameters. In one or more aspects, the PHYprocessor 215 generates and provides RXVECTOR parameters to the MACprocessor 211 to inform the MAC processor 211 of the received packetparameters.

In some aspects, the wireless communication device 200 includes aread-only memory (ROM) (not shown) or registers (not shown) that storeinstructions that are needed by one or more of the MAC processor 211,the PHY processor 215 and/or other components of the wirelesscommunication device 200.

In one or more implementations, the wireless communication device 200includes a permanent storage device (not shown) configured as aread-and-write memory device. The permanent storage device may be anon-volatile memory unit that stores instructions even when the wirelesscommunication device 200 is off. The ROM, registers and the permanentstorage device may be part of the baseband processor 210 or be a part ofthe memory 240. Each of the ROM, the permanent storage device, and thememory 240 may be an example of a memory or a computer-readable medium.A memory may be one or more memories.

The memory 240 may be a read-and-write memory, a read-only memory, avolatile memory, a non-volatile memory, or a combination of some or allof the foregoing. The memory 240 may store instructions that one or moreof the MAC processor 211, the PHY processor 215, and/or anothercomponent may need at runtime.

The RF transceiver 220 includes an RF transmitter 221 and an RF receiver222. The input interface unit 250 receives information from a user, andthe output interface unit 260 outputs information to the user. Theantenna unit 230 includes one or more antennas. When multi-inputmulti-output (MIMO) or multi-user MIMO (MU-MIMO) is used, the antennaunit 230 may include more than one antenna.

The bus 270 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal components ofthe wireless communication device 200. In one or more implementations,the bus 270 communicatively connects the baseband processor 210 with thememory 240. From the memory 240, the baseband processor 210 may retrieveinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The baseband processor 210 can be asingle processor, multiple processors, or a multi-core processor indifferent implementations. The baseband processor 210, the memory 240,the input interface unit 250, and the output interface unit 260 maycommunicate with each other via the bus 270.

The bus 270 also connects to the input interface unit 250 and the outputinterface unit 260. The input interface unit 250 enables a user tocommunicate information and select commands to the wirelesscommunication device 200. Input devices that may be used with the inputinterface unit 250 may include any acoustic, speech, visual, touch,tactile and/or sensory input device, e.g., a keyboard, a pointingdevice, a microphone, or a touchscreen. The output interface unit 260may enable, for example, the display or output of videos, images, audio,and data generated by the wireless communication device 200. Outputdevices that may be used with the output interface unit 260 may includeany visual, auditory, tactile, and/or sensory output device, e.g.,printers and display devices or any other device for outputtinginformation. One or more implementations may include devices thatfunction as both input and output devices, such as a touchscreen.

One or more implementations can be realized in part or in whole using acomputer-readable medium. In one aspect, a computer-readable mediumincludes one or more media. In one or more aspects, a computer-readablemedium is a tangible computer-readable medium, a computer-readablestorage medium, a non-transitory computer-readable medium, amachine-readable medium, a memory, or some combination of the foregoing(e.g., a tangible computer-readable storage medium, or a non-transitorymachine-readable storage medium). In one aspect, a computer is amachine. In one aspect, a computer-implemented method is amachine-implemented method.

A computer-readable medium may include storage integrated into aprocessor and/or storage external to a processor. A computer-readablemedium may be a volatile, non-volatile, solid state, optical, magnetic,and/or other suitable storage device, e.g., RAM, ROM, PROM, EPROM, aflash, registers, a hard disk, a removable memory, or a remote storagedevice.

In one aspect, a computer-readable medium comprises instructions storedtherein. In one aspect, a computer-readable medium is encoded withinstructions. In one aspect, instructions are executable by one or moreprocessors (e.g., 210, 211, 212, 213, 215, 280, 290) to perform one ormore operations or a method. Instructions may include, for example,programs, routines, subroutines, data, data structures, objects,sequences, commands, operations, modules, applications, and/orfunctions. Those skilled in the art would recognize how to implement theinstructions.

A processor (e.g., 210, 211, 212, 213, 215, 280, 290) may be coupled toone or more memories (e.g., one or more external memories such as thememory 240, one or more memories internal to the processor, one or moreregisters internal or external to the processor, or one or more remotememories outside of the device 200), for example, via one or more wiredand/or wireless connections. The coupling may be direct or indirect. Inone aspect, a processor includes one or more processors. A processor,including a processing circuitry capable of executing instructions, mayread, write, or access a computer-readable medium. A processor may be,for example, an application specific integrated circuit (ASIC), adigital signal processor (DSP), or a field programmable gate array(FPGA).

In one aspect, a processor (e.g., 210, 211, 212, 213, 215, 280, 290) isconfigured to cause one or more operations of the subject disclosure tooccur. In one aspect, a processor is configured to cause an apparatus(e.g., a wireless communication device 200) to perform operations or amethod of the subject disclosure. In one or more implementations, aprocessor configuration involves having a processor coupled to one ormore memories. A memory may be internal or external to the processor.Instructions may be in a form of software, hardware or a combinationthereof. Software instructions (including data) may be stored in amemory. Hardware instructions may be part of the hardware circuitrycomponents of a processor. When the instructions are executed orprocessed by one or more processors, (e.g., 210, 211, 212, 213, 215,280, 290), the one or more processors cause one or more operations ofthe subject disclosure to occur or cause an apparatus (e.g., a wirelesscommunication device 200) to perform operations or a method of thesubject disclosure.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processing unit 280 in a wireless communicationdevice. The transmitting signal processing unit 280 of the PHY processor215 includes an encoder 281, an interleaver 282, a mapper 283, aninverse Fourier transformer (IFT) 284, and a guard interval (GI)inserter 285.

The encoder 281 encodes input data. For example, the encoder 281 may bea forward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing device,or may include a low-density parity-check (LDPC) encoder. Theinterleaver 282 interleaves the bits of each stream output from theencoder 281 to change the order of bits. In one aspect, interleaving maybe applied only when BCC encoding is employed. The mapper 283 maps thesequence of bits output from the interleaver 282 into constellationpoints.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may use multiple instances of the interleaver 282 and multipleinstances of the mapper 283 corresponding to the number of spatialstreams (Nss). In the example, the transmitting signal processing unit280 may further include a stream parser for dividing outputs of the BCCencoders or the LDPC encoder into blocks that are sent to differentinterleavers 282 or mappers 283. The transmitting signal processing unit280 may further include a space-time block code (STBC) encoder forspreading the constellation points from the number of spatial streamsinto a number of space-time streams (NsTs) and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming depending onimplementation. When MU-MIMO is employed, one or more of the blocksbefore reaching the spatial mapper may be provided for each user.

The IFT 284 converts a block of the constellation points output from themapper 283 or the spatial mapper into a time domain block (e.g., asymbol) by using an inverse discrete Fourier transform (IDFT) or aninverse fast Fourier transform (IFFT). If the STBC encoder and thespatial mapper are employed, the IFT 284 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may insert cyclic shift diversities (CSDs) to preventunintentional beamforming. The CSD insertion may occur before or afterthe inverse Fourier transform operation. The CSD may be specified pertransmit chain or may be specified per space-time stream. Alternatively,the CSD may be applied as a part of the spatial mapper.

The GI inserter 285 prepends a GI to the symbol. The transmitting signalprocessing unit 280 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 221 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 230. When MIMO or MU-MIMO is employed, the GI inserter 285 and theRF transmitter 221 may be provided for each transmit chain.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processing unit 290 in a wireless communication device.The receiving signal processing unit 290 of the PHY processor 215includes a GI remover 291, a Fourier transformer (FT) 292, a demapper293, a deinterleaver 294, and a decoder 295.

The RF receiver 222 receives an RF signal via the antenna unit 230 andconverts the RF signal into one or more symbols. In some aspects, the GIremover 291 removes the GI from the symbol. When MIMO or MU-MIMO isemployed, the RF receiver 222 and the GI remover 291 may be provided foreach receive chain.

The FT 292 converts the symbol (e.g., the time domain block) into ablock of the constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT) depending on implementation. Inone or more implementations, the FT 292 is provided for each receivechain.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may be a spatial demapper for converting the Fourier transformedreceiver chains to constellation points of the space-time streams, and aSTBC decoder (not shown) for despreading the constellation points fromthe space-time streams into the spatial streams.

The demapper 293 demaps the constellation points output from the FT 292or the STBC decoder to the bit streams. If the LDPC encoding is used,the demapper 293 may further perform LDPC tone demapping before theconstellation demapping. The deinterleaver 294 deinterleaves the bits ofeach stream output from the demapper 293. In one or moreimplementations, deinterleaving may be applied only when BCC encoding isused.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may use multiple instances on the demapper 293 and multipleinstances of the deinterleaver 294 corresponding to the number ofspatial streams. In the example, the receiving signal processing unit290 may further include a stream deparser for combining the streamsoutput from the deinterleavers 294.

The decoder 295 decodes the streams output from the deinterleaver 294and/or the stream deparser. For example, the decoder 295 may be an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

FIG. 4 illustrates a schematic diagram of an example of a format of ahigh efficiency (HE) physical layer convergence procedure (PLCP)protocol data unit (HE PPDU) frame 400. A transmitting STA generates thePPDU frame 400 and transmits the PPDU frame 400 to a receiving STA. Thereceiving STA receives, detects, and processes the PPDU frame 400. ThePPDU frame 400 includes an L-STF field 401, an L-LTF field 402, an L-SIGfield 403, an RL-SIG field 404, an HE-SIG-A field 405, an HE-SIG-B field406, an HE-STF field 407, an HE-LTF field 408, and an HE-DATA field 409.The HE-SIG-A field 405 includes NHESIGA symbols 410, the HE-SIG-B field406 includes NHESIGB symbols 411, the HE-LTF field 408 includes NHELTFsymbols 412, and the HE-DATA field 409 includes NDATA symbols 413. Table1, shown below, describes fields of the PPDU frame 400 in more detail.

TABLE 1 PPDU Frame DFT Subcarrier Element Definition Duration period GISpacing Description Legacy (L)- Non-high 8 μs — — equivalent L-STF of aSTF throughput(HT) to 1,250 kHz non-trigger- Short Training based PPDUfield has a periodicity of 0.8 μs with 10 periods. L-LTF Non-HT Long 8μs 3.2 μs 1.6 μs 312.5 kHz Training field L-SIG Non-HT 4 μs 3.2 μs 0.8μs 312.5 kHz SIGNAL field RL-SIG Repeated Non- 4 μs 3.2 μs 0.8 μs 312.5kHz HT SIGNAL field HE-SIG-A HE SIGNAL A N_(HESIGA) * 3.2 μs 0.8 μs312.5 kHz HE-SIG-A is field 4 μs duplicated on each 20 MHz segment afterthe legacy preamble to indicate common control information. N_(HESIGA)means the number of OFDM symbols of the HE-SIG-A field and is equal to 2or 4. HE-SIG-B HE SIGNAL B N_(HESIGB) * 3.2 μs 0.8 μs 312.5 kHzN_(HESIGB) field 4 μs means the number of OFDM symbols of the HE-SIG-Bfield and is variable. DL MU packet contains HE-SIG-B. SU packets and ULTrigger based packets do not contain HE-SIG-B. HE-STF HE Short 4 or 8 μs— — non- HE-STF of a Training field trigger- non-trigger- based basedPPDU PPDU: has a (equivalent periodicity of to) 1,250 0.8 μs with 5 kHz;periods. A trigger- non-trigger- based based PPDU is PPDU: not sent in(equivalent response to a to) 625 trigger frame. kHz The HE-STF of atrigger- based PPDU has a periodicity of 1.6 μs with 5 periods. Atrigger-based PPDU is an UL PPDU sent in response to a trigger frame.HE-LTF HE Long N_(HELTF) * 2xLTF: supports 2xLTF: HE PPDU Training field(DFT 6.4 μs 0.8, 1.6, (equivalent may support period + 4xLTF: 3.2 μs to)156.25 2xLTF mode GT) μs 12.8 μs  kHz; and 4xLTF 4xLTF: mode. 78.125 kHzIn the 2xLTF mode, HE- LTF symbol excluding GI is equivalent tomodulating every other tone in an OFDM symbol of 12.8 μs excluding GI,and then removing the second half of the OFDM symbol in time domain.N_(HELTF) means the number of HE- LTF symbols and is equal to 1, 2, 4,6, 8. HE-DATA HE DATA N_(DATA) * 12.8 μs  supports 78.125 kHz  N_(DATA)means field (DFT 0.8, 1.6, the number of period + 3.2 μs HE data GI) μssymbols.

FIG. 5 illustrates a schematic diagram of an example of a DL OFDMA PPDU500 transmission to a set of STAs. The AP transmits a DL OFDMA PPDU(e.g., 500) in a HE PPDU format (e.g., 400). The HE PPDU format 400 iscomposed of the Legacy PLCP 502 (which consists of STF, LTF and SIGsymbols that are modulated with FFT size of 64 on 20 MHz sub-channel andis duplicated every 20 MHz if the DL OFDMA PPDU has wider bandwidth than20 MHz), the HE PLCP (which consists of all or part of HE SIG-A 503using FFT size of 64 and duplicated on all the 20 MHz sub-channels thatthe DL OFDMA PPDU consists of, and HE-STF 505, HE-LTF 505, HE SIG-B 504using FFT size of either 64 or 256 and modulated over the entirebandwidth of the DL OFDMA PPDU) and the PSDU 506 (which has payloads formultiple STAs, and is modulated using FFT size of 256).

In FIG. 5, the payloads are for STA1, STA2, STA3, and STA4. The APtransmits the payloads through sub-bands of possibly varying bandwidth,and possibly non-contiguous bands for a given STA. The bandwidth ofindividual sub-bands are the same due to the size of the payload sent toeach STA and based on the AP's decision. Each PSDU (e.g., 514, 515, 516,517) contains the payload that is destined to the STA (e.g., STA1, STA2,STA3, STA4) plus the necessary MAC padding and/or PHY padding (e.g.,508, 511, 513). The bandwidth in this embodiment may be 20 MHz, whereeach of the sub-bands have 5 MHz bandwidth, or the bandwidth may be 40MHz, where each of the sub-bands have 10 MHz bandwidth, or the bandwidthmay be 80 MHz, where each of the sub-bands have 20 MHz bandwidth.

In one aspect of the disclosure, a frame may refer to a MU-MIMO frame,an OFDMA frame, a high efficiency (HE) OFDMA frame, an OFDMA PPDU, a HEOFDMA PPDU, a PPDU, a MU PPDU or vice versa. In one aspect, a frame maybe a downlink (DL) frame or an uplink (UL) frame. In one aspect, a DLOFDMA PPDU (e.g., 500) includes a header (e.g., 501) and a payload(e.g., 506). In one aspect, HE refers to the IEEE 802.11axspecification, 802.11ax, 11ax or vice versa.

FIG. 6 illustrates a schematic diagram of an example of a DL OFDMA PPDU600 transmission to a set of STAs. FIG. 6 shows a similar transmissionas in FIG. 5 except that the PSDU for each STA contains a payload (e.g.,507, 509, 510, 512) without excessive MAC padding (but possibly theshort PHY padding is included). Due to avoidance of the MAC padding, thePSDUs have variable size. In this respect, the PSDU with the longestsize, determines the size of the overall DL OFDMA PPDU 600. Thebandwidth in this embodiment may be 20 MHz, where each of the sub-bandshave 5 MHz bandwidth, or the bandwidth may be 40 MHz, where each of thesub-bands have 10 MHz bandwidth, or the bandwidth may be 80 MHz, whereeach of the sub-bands have 20 MHz bandwidth. In the latter case whereeach PSDU occupies a 20 MHz sub-band, note that the AP places thelongest PSDU on the primary channel of the BSS operation (to avoidambiguity in channel availability among the STAs that are associatedwith the same AP and belong to the same BSS). In this case, each PSDUhas a different length and individual PSDU length is indicated in eitherHE SIG-A or HE SIG-B (e.g., 501). The methods to indicate the length ofeach PSDU may vary by design. For instance, in one embodiment, each PSDUor payload length is explicitly indicated by the absolute values withPSDU length in bytes. For instance, in FIG. 6, the length of the PSDUthat is destined to each STA is encoded within HE SIG-A or HE SIG-B interms of the total bytes of the PSDU (along with other attributes ofeach PSDU such as a modulation coding scheme (MCS), the number ofspatial streams (NSS), etc.). In another embodiment, each PSDU length isindicated in absolute values of the OFDM symbols. For instance, in FIG.6, the length for PSDU that is destined to each STA is encoded within HESIG-A or SIG-B in terms of the number of OFDM symbols that the PSDUspans (along with other attributes of each PSDU such as MCS, NSS, etc.).

FIG. 7 illustrates a schematic diagram of an example of a DL OFDMA PPDU700 transmission to a set of STAs. In this example, the bandwidth ofindividual sub-bands are the same due to the size of the payload sent toeach STA and based on the AP's decision. FIG. 7 shows a transmission asin FIG. 6, except that the PSDU for each STA does not contain excessiveMAC padding (but possibly short MAC and/or PHY padding are included). Inan embodiment, multiple PSDUs may be within a single sub-band, whereeach PSDU occupy a time segment. Each PSDU contains the payload that isdestined to the STA but with no or low amounts of MAC padding and PHYpadding (e.g., not exceeding a threshold amount of padding that isconsidered excessive). The AP avoids excessive MAC padding and insteadadds another PSDU (e.g., 702, 704), equivalently another PSDU in a newtime-segment, in each sub-band that has shorter length compared to thelength of the DL OFDM PPDU 700. Due to the avoidance of MAC padding, thePSDUs may have variable size, but in order to align the ending ofmultiple PSDUs, the AP may assign shorter payloads to other STAs in asub-band. In order to add a subsequent PSDU in a sub-band, the AP firstadds a HE STF and/or HE LTF (e.g., 701, 703), which helps in the PHYprocessing at the receiving STA. Then the AP adds the subsequent PSDU(e.g., 702, 704) after the added HE STF/LTF symbols.

The bandwidth in this embodiment may be 20 MHz, where each of thesub-bands have 5 MHz bandwidth, or the bandwidth may be 40 MHz, whereeach of the sub-bands have 10 MHz bandwidth, or the bandwidth may be 80MHz, where each of the sub-bands have 20 MHz bandwidth. Therefore, inone embodiment, additional HE STF/LTF symbols appear in the sub-bandportion of the payload (e.g., 506) of the PPDU 700, where the additionalHE STF/LTF symbols appear on a set of resource-units, a set of 20 MHzsub-channels, or the entire bandwidth of the PPDU by the AP's decision.A STA that receives such PPDU becomes aware of the presence of theadditional HE STF/LTF symbols from one or multiple sub-fields within thefirst HE SIG-A or SIG-B symbols in the header (e.g., 501) and alsobecomes aware that its payload (e.g., 506), if there is any, appearsafter which of the HE STF/LTF symbol(s). In this embodiment, in order toadd another PSDU to the end of a first PSDU, the AP first adds HE STFand/or HE LTF (right after the end of the first PSDU in the sub-band)and then adds the PSDU that is destined to another STA. For instance inFIG. 7, the PSDU destined to STA1 (e.g., 507) is followed by anotherpayload to another STA (e.g., a payload to STA5 as in the figure) in thesame sub-band that is assigned to STA1. In order to do this, the AP addsHE STF and/or HE LTF(s) symbols after the first PSDU and then adds thePSDU for STA5 (which may be sometimes referred to as a “subsequentPSDU”, or a “PSDU in the second time-segment”). Similarly, in the samesub-band that the AP has assigned to STA3 (e.g., 510), the AP adds HESTF and/or HE LTF (e.g., 703) and a PSDU (e.g., 704) intended for STAG.However, in the same sub-band that the AP has assigned to STA4 (e.g.,512), the AP may not be able to add another PSDU for another STA and mayresort to moderate padding (e.g., 513) of the PSDU to STA4. Note thatthe HE LTF may have multiple symbols depending on the number of spatialstreams that each PSDU carries. In other embodiments, the AP may not addany HE STF/LTF if the subsequent PSDU is not beamformed. The necessarylength information for each PSDU (e.g., the PSDU to STA1, STA2, STA3,STA4, STA5, STA6) and the particularly for PSDU to the subsequent PSDUs(e.g., STA5 and STA6) are indicated in HE SIG-A or HE SIG-B as describedbelow. In another embodiment, a subsequent PSDU or a PSDU in the secondtime-segment is added to each sub-band or each resource-unit (RU). Inanother embodiment, a subsequent PSDU or a PSDU in the secondtime-segment is added to each 20 MHz sub-channel or to each sub-band orRU such that the time position of HE STF/LTF symbols at the beginning ofeach subsequent PSDU is aligned with the time position of HE STF/LTFsymbols at the beginning of other subsequent PSDUs. This would mean thatthe length of each first PSDU in each 20 MHz sub-channel or sub-band isthe same as the length of other first PSDUs in other 20 MHz sub-channelsor sub-bands. In another embodiment, another subsequent PSDU or a PSDUin the next time-segment is added to each 20 MHz sub-channel or sub-bandsuch that the time position of HE STF/LTF symbols at the beginning ofeach of such subsequent PSDUs is aligned with the time position of HESTF/LTF symbols at the beginning of other such subsequent PSDUs. In theabove embodiments, where each 20 MHz sub-channel or sub-band that hasone or more subsequent PSDUs, and wherever the additional HE STF symbolsare aligned across the full bandwidth, the number of HE STF and HE LTFsymbols whose beginning are aligned, are the same across 20 MHzsub-channels or sub-bands, and the type of such HE LTF symbols (such asthe length of each HE LTF symbol), are the same across 20 MHzsub-channel or sub-bands (i.e. they are all 1×LTF, 2×LTF or 4×LTF).

In an embodiment, where each 20 MHz sub-channel carries one or moreadditional HE STF/LTF symbols, and where each additional HE STF/LTFsymbol in each 20 MHz sub-channel is aligned across the full bandwidth,the partitioning of bandwidth to the resource-units between twoconsecutive HE STF/LTF symbols may vary such that the resource-unitsafter an additional HE STF/LTF may not be the same with the partitioningof the resource-units before the additional HE STF/LTF. A STA thatreceives such PPDU becomes aware of the presence of the additional HESTF/LTF symbols and the resource-unit partitioning between a consecutivepair of HE STF/LTF symbols from one or multiple sub-fields within thefirst HE SIG-A or SIG-B symbols in 501. In an embodiment, one or morefields within HE SIG-A/SIG-B indicate the presence, number, and/orlocation of the additional HE STF/LTF symbols or may include the numberand duration of the time-segments, where each time-segment appearsbetween two consecutive HE STF/LTF symbols. In an embodiment, there aremultiple portions within HE SIG-B where each portion indicates theresource-unit partitioning between two consecutive HE STF/LTF symbols(i.e. the resource-units for a time-segment). In an embodiment, theCommon field and the User Specific field of one time-segment appeartogether and possibly followed by the Common field and the User Specificfield of a subsequent time-segment. In an embodiment, the Common fieldof one time-segment includes the duration or length of the sametime-segment and may include an indication of whether there is asubsequent time-segment and possibly the length of a subsequenttime-segment. In an embodiment, the cyclic-prefix (CP) or guard-interval(GI) in one time-segment may be different with the CP or GI in anothertime-segment within the same PPDU. In an embodiment, the number of HESTF and HE LTF symbols at the beginning of a time-segment may bedifferent from the number of HE STF and HE LTF symbols at the beginningof another time-segment within the same PPDU. In an embodiment, the typeof HE LTF symbols (such as the length of each HE LTF symbol) at thebeginning of a time-segment may be different from the type of HE LTFsymbols at the beginning of another time-segment within the same PPDU.

In one or more aspects, the HE STF and HE LTF symbols that fall betweentwo consecutive PSDUs (such as the HE STF/LTF symbols between the PSDUfor STA1 and PSDU for STA5), the total length of the HE STF and HE LTFsymbols may be an integer multiple of the sum of the length of the OFDMsymbol in the payload part (e.g., 506) of the DL OFDMA PPDU 700 plus theassociated GI. For instance, if the OFDM symbols for the payload part ofthe DL OFDMA PPDU uses FFT=256 and the length of the OFDM symbol plusthe GI is 16 μs, then the total length of the HE STF and HE LTF symbolsmay be an integer multiple of 16 μs. For instance, let's consider thecase where HE STF duration is 4 μs and HE LTF duration is 8 μs and theGI for the payload section of the DL OFDMA PPDU is 3.2 μs (hence totalduration of OFDM symbols with FFT=256 is 12.8+3.2=16p). Then, if thepayload for STA5 or STA6 in FIG. 7 has NSS=1, e.g., a singlespatial-stream, then one possibility for the total length of the HESTF/LTF symbols right before the start of the payload of STA5 and STA6is to repeat HE STF symbol twice followed by an HE LTF symbol, which intotal the length of (STF, STF, LTF) is 16 μs. For other GI values andfor larger number of spatial streams there are more possibilitiesdepending on implementation.

However, for the embodiments based on FIG. 7, the presence of HE STFand/or HE LTF depends on whether the subsequent PSDU is beamformed ornot, and how many spatial streams are carried in the subsequent PSDU.For instance, if the subsequent PSDUs, such as the PSDU for STA5 andSTAG in FIG. 7, has NSS=1 and (and none of the PSDUs in the sub-band arebeamformed to their respective STA, e.g., the TX-VECTOR BEAMFORMEDparameter indicates no beamforming), then the AP can place thesubsequent PSDU without any HE STF or HE LTF symbols. This may be due tothe fact that since HE STF and HE LTF symbols are usually beamformed andif the PSDU is not beamformed, hence the receiving STA can use earlierSTF and LTF symbols (such as Legacy STF or LTF symbols or the HE STF/LTFsymbols at the beginning of the PPDU) to adjust the PHY operationparameters in order to optimally receive its PSDU. The presence of HESTF and HE LTF for the subsequent PSDUs (e.g., the HE STF/LTF in betweentwo PSDUs as shown in FIG. 7) may implicitly be obtained from theRX-VECTOR BEAMFORMED parameter, where when it indicated no beamforming,the receiver knows that the subsequent PSDU does not start with any HESTF/LTF symbols. In some embodiments, even if the subsequent PSDUs arenot beamformed (e.g., the TX-VECTOR BEAMFORMED parameter indicates nobeamforming), a HE LTF symbol may be present to obtain a more preciseand a fresher channel estimation for decoding the subsequent PSDU.

In some aspects, the STAs that have their PSDUs starting in the middleof the payload section of DL OFDMA PPDU (such as STA5 in FIG. 7), neednot decode all the OFDM symbols that come before the start of theirPSDU. The following explains the method to save power consumption byfast-forwarding to the beginning of their desired PSDU or time-segment.As described below, whether a subsequent PSDU or time-segment exists ina sub-band, and to which STA the subsequent PSDU or time-segment belongsto, and the start of each subsequent PSDU or time-segment (or the startof HE STF/LTF that comes before a subsequent PSDU or time-segment) areindicated in HE SIG-B or HE SIG-A fields. Hence, the STA that has asubsequent PSDU, or has a payload in a subsequent time-segment, knowsfrom what OFDM symbol the PSDU (or HE STF/LTF symbols right before thePSDU) starts. Hence, the STA can skip to the start of the PSDU byavoiding PHY baseband processing of the OFDM symbols that do not haveany assignment or payload for the STA. This may be performed by skippingthe received signal in time-domain (e.g., not performing FFT processing)for the duration that is equivalent to the duration of the PSDU that hasappeared before the assigned PSDU or the right time-segment. Forinstance, in reference to FIG. 7, STA5 whose PSDU appears as asubsequent PSDU (after the PSDU of STA1) need not perform full PHYprocessing for all the received OFDM symbols. Alternatively, STA5 canskip processing during the duration indicated by Tskip_STA5 (e.g.,simply skip processing these OFDM symbols in time domain, withoutperforming any FFT processing or the subsequent processing), where STA5can start full PHY processing right at the beginning its assigned PSDUor right from HE STF/LTF symbols that come right before its PSDU.Similarly, STA6 whose PSDU appears as a subsequent PSDU (after the PSDUof STA3) need not perform full PHY processing for all the received OFDMsymbols. Alternatively, STA6 can skip processing during the durationindicated by Tskip_STA6 (e.g., simply skip processing these OFDM symbolsin time domain, without performing any FFT processing or the subsequentprocessing), where STA6 can start full PHY processing right at thebeginning its assigned PSDU or right from HE STF/LTF symbols that comeright before its PSDU. Such technique offers power saving advantages tothe STAs where their PSDU appear as subsequent PSDU.

In some implementations, there may be more than two PSDUs in a sub-band,and based on the explanation above, there may be a set of HE STF and/orHE LTF for each PSDU. As shown in FIG. 7, at most two PSDUs exist persub-band. In one aspect, multiple PSDUs can exist in a sub-band, whereeach subsequent PSDU may start with HE STF and/or HE LTF symbolsdepending on NSS and whether TXVECTOR BEAMFORMED parameter indicatesbeamforming for the PSDU.

The presence of HE STF/LTF symbols for each subsequent PSDU depends onthe value of NSS, and whether TXVECTOR BEAMFORMED parameter indicatesbeamforming or not. It may be possible that the first subsequent PSDUhas NSS=1 and it is not beamformed, hence does not have any HE STF/LTFsymbols. But the second subsequent PSDU is either beamformed or hasNSS>1, hence starts with HE STF and/or HE LTF symbols. Also, it ispossible that the first subsequent PSDU has NSS>1 or it is beamformed,hence it has HE STF and/or HE LTF symbols, but the second subsequentPSDU NSS=1 and it is not beamformed.

In some aspects, the start of non-subsequent PSDUs, such as the PSDUsfor STA1, STA2, STA3 and STA4 is known to be right after the PHY header(e.g., right after HE SIG-B or HE LTF symbols). Since this is implicitlygiven, the start of the non-subsequent PSDUs is not explicitlyindicated. However, the beginning of the subsequent PSDUs (such as thePSDU destined to STA5 and STA6 in FIG. 7) may be indicated in HE SIG-Aor HE SIG-B, along with other attributes of the PSDU (such as theidentification of the STA that the PSDU belongs to and the PHYattributes of the PSDU). There are multiple ways to do so as explainedbelow.

FIG. 8 illustrates a schematic diagram of an example of a sequence 800to indicate the presence and attributes of subsequent PLCP service dataunits (PSDU)s along with the PSDU attributes. The “PSDU attributes” inFIG. 8 may be in a form of “SU PSDU attributes” or “MU PSDU attributes.”For “MU PSDU attributes,” a MUSU field (described below) may appear as asub-field of “SU PSDU attributes” and “MU PSDU attributes.” The sequenceof data shown in FIG. 8 may appear in HE SIG-A or HE SIG-B symbols. Inthis embodiment, the attributes of all the PSDUs appear in the order ofincreasing index of the sub-bands. For instance the first “SU PSDUattributes” indicates the attributes of the first sub-band (e.g., 801),and the second “SU PSDU attributes” indicates the attributes of thesecond sub-band (e.g., 803), and the last “SU PSDU attributes” indicatesthe attributes of the last sub-band. As shown in FIG. 8, after each PSDUattribute, there is a single-bit field which is called “More PSDU” field(e.g., 802, 805) and it simply states whether there is a subsequent PSDUin the same sub-band or not. If the “More PSDU” field is equal to zero,it means there is no subsequent PSDU in the sub-band, and if the “MorePSDU” field is equal to one, it means there is a subsequent PSDU in thesub-band, which follows with the “SU PSDU attributes” and the start ofthe PSDU (e.g., 803, 806). In other another embodiment, if the “MorePSDU” field is equal to one, it means there is a subsequent PSDU in thesub-band, which follows with the “SU PSDU attributes”, the start of thePSDU, and another single-bit “More PSDU” field. The value of this “MorePSDU” may be zero or one, and if it is one it indicates that there is asecond subsequent PSDU in the sub-band and then another “SU PSDUattributes”, the start of PSDU, and another “More PSDU” field follows.In other embodiments, the “More PSDU” field (e.g., 802, 805) may appearas a sub-field in “SU PSDU attributes” as well as “MU PSDU attributes”(which will be explained later), and would have the same meaning asexplained above. In an alternative embodiment, where there is always oneor more subsequent PSDUs or subsequent time-segments in each sub-band orresource-unit (RU), and each duration of a specific time-segment (i.e.first time-segment, second time-segment, etc.) is the same across allsub-bands or RUs, the set of PSDU attributes of the next time-segmentappears after the set of PSDU attributes of the previous time-segment,along with a time-reference to the beginning of each next time-segment.For instance, if there are two time-segments, where the size of thefirst time-segment is the same across all RUs and the size of the secondtime-segment is the same across all RUs, then in HE SIG-A or SIG-B, theset of the PSDU attributes of the second time-segment appears after theset of the PSDU attributes of the first time-segment, as well as atime-reference to the beginning of the second time-segment (e.g. in formof the number of OFDMA symbols).

The “SU PSDU attributes” field contains several sub-fields such as: MCS(4 bits), AID (12 bits), Coding (1 bit), NSTS (3 bits), STBC (1 bit),SU-Beamformed (1 bit). In other embodiments, instead of AID, Partial AID(PAID) may be used. While the order of the sub-fields is not crucial,appearing the MCS sub-field as the first sub-field in the “SU PSDUattributes” would be beneficial as described below. The value for Codingis BCC or LDPC. The values for NSTS (or NSS) is zero to seven, whichindicates the number of spatial streams. The field of AID (which is anassociation identifier) is an identification that is assigned to a STAby the AP at the time of association. The values for MCS range from zeroto nine based on the number of MCS defined in IEEE 802.11ac and othervalues are reserved. However, in subsequent specifications of IEEE802.11 values larger than nine may be used for newly introduced MCS. Inan embodiment, the value of MCS=15 is used to indicate a special meaningas described below. The field “start of PSDU” (e.g., 803, 806) indicatesthe OFDM symbol index where a subsequent PSDU starts. The indexing ofthe OFDM symbols start right after the PHY header, e.g., right after thelast symbol of the HE PHY header (which may be HE SIG-B or HE LTFsymbols). The index of the first OFDM symbol after the HE PHY headersymbols is set to zero, and the index of the next OFDM symbolsincrements by one. The size of “start of PSDU” field may be eight bits.

FIG. 9 illustrates an example of a DL OFDMA PPDU 900 transmission to aset of STAs. FIG. 9 shows a transmission as in FIG. 7, except that thePSDU for STA2 continues to a separate sub-band shared by STA5. In thisrespect, two or more consecutive sub-bands are assigned to a single PSDU(e.g., the PSDU for STA2 covers more than one sub-band). As the exampleshown in FIG. 9, where the assignment for STA2 covers two consecutivesub-bands (e.g., 509, 901), the “SU PSDU attributes” for the secondsub-band appears in a shorter form. As indicated above, the “SU PSDUattributes” start with the field MCS. If the value of MCS is set to 15,it indicates that the same “SU PSDU attributes” as the previous sub-bandis being applied, and the remaining sub-fields of the “SU PSDUattributes” are skipped. For instance in the example of FIG. 9, thesequence of “SU PSDU attributes” are as follows: “SU PSDUattributes”{MCS, STA1's AID, . . . }+{More PSDU=1}+“SU PSDUattributes”{MCS, STA4's AID, . . . }+{start of PSDU: STA4}+“SU PSDUattributes”{MCS, STA2's AID, . . . }+{More PSDU=0}+“SU PSDUattributes”{MCS=15}+{More PSDU=1}+“SU PSDU attributes”{MCS, STA5's AID,. . . }+{start of PSDU: STA5}+“SU PSDU attributes”{MCS, STA3's AID, . .. }+{More PSDU=0}. If more than two consecutive sub-bands are used for asingle PSDU, then for the first sub-band all the sub-fields of the “SUPSDU attributes” appear, and for the second sub-band only the MCSsub-field appears with value equal to 15, and for the third sub-bandonly the MCS sub-field appears with value equal to 15, and so on untilthe last sub-band. Note that instead of the value of 15, other valuesfrom 9 to 14 may be used, or any other value that does not convey anyMCS index.

FIG. 10 illustrates a schematic diagram of an example of a sequence 1000to indicate the presence and attributes of subsequent PSDUs along withthe PSDU attributes. In one aspect, the sequence 1000 may indicatepresence of subsequent PSDUs in a sub-band(s) along with the PSDUattributes. The “PSDU attributes” shown in FIG. 10 may be in a form of“SU PSDU attributes” or “MU PSDU attributes.” In case of “MU PSDUattributes,” a MUSU field (described below with respect to FIG. 12) mayappear as a sub-field of “SU PSDU attributes” and “MU PSDU attributes.”The sequence 1000 of data shown in FIG. 10 may appear in the HE SIG-A orHE SIG-B symbols. In this embodiment, the attributes of all the PSDUsappear in the order of increasing index of the sub-bands. For instancethe first “SU PSDU attributes” 1001 indicates the attributes of thefirst sub-band, and the second “SU PSDU attributes” 1002 indicates theattributes of the second sub-band, and the last “SU PSDU attributes”1003 indicates the attributes of the last sub-band. As shown in FIG. 10,the PSDU attribute for all the sub-bands appear in order. If two or moreconsecutive sub-bands are used for a single PSDU then value of MCS=15 isused to indicate that the PHY attributes of the two or more sub-bandsare the same (and the remaining sub-fields of the “SU PSDU attributes”that starts with MCS=15 is skipped as explained above). After the “SUPSDU attributes” for all the sub-bands that appear in order, the “SUPSDU attributes” for the subsequent PSDUs are indicated. To do so, the“SU PSDU attributes” appear along with Sub-band ID (SID) and “start ofPSDU” (e.g., 1004, 1005). The value and meaning of “start of PSDU” is asexplained above. The sub-field SID is an index of the sub-bands (thathave a subsequent PSDU). The number of bits assigned to SID depends onthe number of sub-bands in the PPDU. For instance, if the PPDU bandwidthis 20 MHz, and the bandwidth of each sub-band is 5 MHz, then SID has twobits. If the PPDU bandwidth is 40 MHz or 80 MHz, and the bandwidth ofeach sub-band is 5 MHz, then SID has three or four bits. If the PPDUbandwidth is 20 MHz or 40 MHz or 80 MHz, and the bandwidth of eachsub-band is 2.5 MHz, then SID has three, four or five bits subsequently.In an alternative embodiment, where there is always one or moresubsequent PSDUs or subsequent time-segments in each sub-band or RU, andthe duration of a specific time-segment is the same across all RUs, theset of PSDU attributes of the next time-segment appears after the set ofPSDU attributes of the previous time-segment, as shown in FIG. 10 butwithout SID indication (since all RUs have a subsequent PSDU) and where“start of PSDU” appears only once in the sequence as a time-reference tothe beginning of each next time-segment. For instance, if there are twotime-segments, the sequence in FIG. 10 would be the set of PSDUattributes of the first time-segment follows by the set of PSDUattributes of the second time-segment, along with a “start of PSDU”subfield that is the time-reference to the beginning of each secondtime-segment.

FIG. 11 illustrates an example of a DL OFDMA PPDU 1100 transmission to aset of STAs. FIG. 11 shows that if the AP has DL MU MIMO capability, theAP may use one of several sub-bands to perform DL MU MIMO transmissionsto the STAs that are DL MU MIMO capable, and use the remaining of thesub-bands to other STAs for a non DL MU MIMO transmission (ornon-MU-MIMO transmission). In this embodiment, the bandwidth ofindividual sub-bands are not the same (e.g., 1103, 1104, 1105), and a DLMU MIMO technique has been used in the top 20 MHz sub-band to sendindividual PSDUs within the same 20 MHz bandwidth to STA1, STA2, andSTA3 (e.g., 1102). To uniquely indicate and address SU and MUtransmissions within a DL OFDMA PPDU, the following methods aredescribed.

In the first solution to uniquely indicate and address SU and MUtransmissions within a DL OFDMA PPDU, a new field called MU Sub-band isused where SID and GID (Group ID as in IEEE 802.11ac GID) are used. Thepair of (SID, GID) indicates the GID that a sub-band is using. Note thata given GID value, such as GID=0, is used to indicate SU transmission,e.g., no DL MU MIMO transmission. However, other GID values indicate DLMU MIMO transmission to the STAs that are a member of the given GID. Themembership of each GID is pre-announced by AP. For instance, if the PPDUbandwidth is 20 MHz, and the bandwidth of each sub-band is 5 MHz, thenSID has two bits and above-mentioned sequence appears as: (00,GID0),(01,GID1), (10,GID2), (11,GID3), where GID0, GID1, GID2, and GID3 arevalues for GID and may be zero to indicate SU transmission, or may beother values to indicate DL MU MIMO transmission to a set of STAs. Theabove sequence may appear in HE SIG-A or HE SIG-B (e.g., 1101).

Moreover, in case that none of the sub-bands have DL MU MIMOtransmission, a single field is defined (denoted by SIDMU) thatindicates whether there is any DL MU MIMO transmission, in which casethe above sequence follows, or indicates that there is no DL MU MIMOtransmission, in which case there is no need that the above sequencefollows since all the GID values would indicate SU transmission (e.g.,GID=0). Therefore, the following sequence of fields is provided:{SIDMU}+(SID0,GID0)+(SID1,GID1)+(SID2,GID2)+ . . . If SIDMU=0 (e.g., noMU transmission) then the sequence of (SID,GID) does not follow, andSIDMU=1 then the sequence of (SID,GID) follows, e.g.,{SIDMU=1}+(SID0,GID0)+(SID1,GID1)+(SID2,GID2)+ . . . where some of GIDvalues is zero (e.g., SU transmission) and some are non-zero indicatingGID that two or more STAs are member of it. The above sequence onlyindicates the presence of DL MU MIMO transmission. Subsequently, in thesame HE SIG-A or HE SIG-B (e.g., 1101), the sequence of “SU PSDUattributes” may appear.

Note that in this embodiment, since both SU and MU MIMO transmissionsare possible, the field of “PSDU attributes” is different for SU and MUMIMO. For the sequence of “PSDU attributes”, both embodiments as in FIG.8 and FIG. 10 can be used. In either of the embodiments, the “PSDUattributes” for SU case is the same as explained above, hence denoted as“SU PSDU attributes.” However for those sub-bands that have MU MIMOtransmissions their “PSDU attributes” is as follows (denoted by “MU PSDUattributes”): first GID (6 bits) appears, followed by NSTS (3 bits pereach STA) for all the STAs that belong to the GID, followed by thefollowing sub-fields only for those STAs that have non-zero NSTS: AID(12 bits per each STA), MCS (4 bits per each STA), Coding(1 bit per eachSTA), and Length (16-19 bits per each STA).

If two or more consecutive sub-bands are used for the same DL MU MIMOtransmission, then for the second and subsequent sub-bands, the “MU PSDUattributes” starts with a given GID value, e.g., GID=62, which indicatesthat the “MU PSDU attributes” of the sub-band is the same as “MU PSDUattributes” of the previous sub-band. In this situation, the remainingsub-fields of “MU PSDU attributes” are skipped and not presented. As anexample, the “MU PSDU attributes” for a DL MU MIMO transmission thatappear on three consecutive sub-bands are: {GID, (NSTS, AID, MCS,Coding, Length) for each STA in the GID with non-zeroNSTS}+{GID=62}+{GID=62}.

Note that instead of GID=62, GID=0 (or the same GID value that is usedto indicate SU transmission) can be used that similarly may indicate theabove meaning. While GID=0 is used for SU transmission, when GID=0appears after a sub-band with a non-zero GID that indicates MU MIMOtransmission, it unambiguously may indicate that the “MU PSDUattributes” of the sub-bands is the same as the “MU PSDU attributes” ofthe prior sub-band and the remaining sub-fields of “MU PSDU attributes”of that sub-band is skipped. The approach of reusing the GID value of SUleaves more GID values to be used for MU MIMO transmission.

In another embodiment, “MU PSDU attributes” may be represented as: NSTS(3 bits per each STA) for all the STAs that belong to the GID, followedby the following sub-fields only for those STAs that have non-zero NSTS:AID (12 bits per each STA), MCS (4 bits per each STA), Coding(1 bit pereach STA), and Length (16-19 bits per each STA).

In one embodiment, the length of HE SIG-B associated with MU MIMOtransmission is shorter than the length of HE SIG-B associated with theSU MIMO transmission.

FIG. 12 illustrates a schematic diagram of an example of a sequence 1200to indicate the presence of sub-bands with several PSDU attributes(e.g., 1201, 1202, 1203). In one aspect, the sequence 1200 may indicatepresence of sub-bands with DL MU MIMO PSDUs in a sub-band(s) along withthe PSDU attributes. The “PSDU attributes” shown in FIG. 12 may be in aform of “SU PSDU attributes” or “MU PSDU attributes.” In one or moreaspects, a MUSU field may appear as a sub-field of “SU PSDU attributes”and “MU PSDU attributes.” In one aspect, FIG. 12 illustrates a secondsolution to uniquely indicate and address SU and MU transmissions withina DL MU MIMO or OFDMA PPDU.

In FIG. 12, for each sub-band, a single-bit field denoted by MUSU isused where MUSU=0 indicates SU transmission (indicating OFDMAtransmission), and MUSU=1 indicates MU MIMO transmission. Then the PSDUattributes are as follows.

-   -   If MUSU=0, the “SU PSDU attributes” follow as described in the        embodiments related to FIG. 8 and FIG. 10. For instance, in FIG.        11, the MUSU subfield for each 20 MHz sub-channel 1103, 1004 and        1105 is set to zero since they are not MU-MIMO. With such        indication, one or more “SU PSDU attributes” follow depending on        the number of assignments in each 20 MHz sub-channel.    -   If MUSU=1, the “MU PSDU attributes” follow as described above.        For instance, in FIG. 11, the MUSU subfield for the top 20 MHz        sub-channel 1102 is set to one since it is MU-MIMO. With such        indication, two or more “MU PSDU attributes” follow depending on        the number of STAs that have assignments in the top 20 MHz        sub-channel (in the example of FIG. 11, three “MU PSDU        attributes” follow).    -   If two or more sub-bands are used for a PSDU for a STA, then the        value of MCS=15 is used to indicate that the “SU PSDU        attributes” of the second (e.g., 1202) and next sub-bands (e.g.,        1203) is the same as the “SU PSDU attributes” of the prior        sub-band (e.g., 1201) and the remaining sub-fields of “SU PSDU        attributes” of that sub-band is skipped and not presented        (similar to the description given for the embodiments related to        FIG. 8 and FIG. 10).    -   If two or more sub-bands are used for a DL MU MIMO transmission,        then the value of GID=62 is used to indicate that the “MU PSDU        attributes” of the second (e.g., 1202) and next sub-bands (e.g.,        1203) is the same as the “MU PSDU attributes” of the prior        sub-band (e.g., 1201) and the remaining sub-fields of “MU PSDU        attributes” of that sub-band is skipped and not presented        (similar to the description given above).    -   Note that instead of GID=62, GID=0 (or the same GID value that        is used to indicate SU transmission) can be used that similarly        may indicate above meaning. While GID=0 is used for SU        transmission, when GID=0 appears after a sub-band with a        non-zero GID that indicates MU MIMO transmission, it        unambiguously may indicate that the “MU PSDU attributes” of the        sub-bands is the same as the “MU PSDU attributes” of the prior        sub-band and the remaining sub-fields of “MU PSDU attributes” of        that sub-band is skipped. The approach of reusing the GID value        of SU leaves more GID values to be used for MU MIMO        transmission.

In some embodiments, to uniquely indicate and address SU and MUtransmissions within a DL MU PPDU, the MUSU subfield discussed aboveappears in HE SIG-A symbol (e.g., 405, 1101). As indicated above, theMUSU subfield may be a single-bit subfield where it indicates whether agiven resource unit (RU) carries MU-MIMO PSDUs or SU PSDU. In oneexample, as shown in FIG. 12, the MUSU subfield are specific to RUs withbandwidth 20 MHz. The MUSU subfield may indicate whether RUs withbandwidth 20 MHz, 40 MHz, 80 MHz and 160 MHz carry MU-MIMO PSDUs. In oneaspect, each of 20 MHz, 40 MHz, 80 MHz and 160 MHz is an example of afull bandwidth of a MU-MIMO transmission. In some embodiments, the MUSUsubfield has multiple bits, where each bit is for one 20 MHz RU andindicates whether the associated 20 MHz sub-band carries MU-MIMO PSDUsor not. As an example, the MUSU subfield would have length 1, 2, 4, and8 bits respectively for 20 MHz (MUSU=b0), 40 MHz (MUSU=b0,b1), 80 MHz(MUSU=b0, . . . , b3) and 160 MHz (MUSU=b0, . . . , b7), where each bitindicates whether the corresponding 20 MHz RU has MU-MIMO PSDUs (MU-MIMOassignments) or SU PSDUs. When the corresponding bit is set to a TRUEvalue, it would indicate that the 20 MHz sub-channel (or equivalentlythe 20 MHz RU) carries MU-MIMO PSDUs, otherwise it would indicate thatthe PSDUs within the corresponding 20 MHz sub-channel are SU PSDUs (i.e.one or more SU PSDUs are assigned to narrower RUs within the 20 MHzsub-channel). In some embodiments, the above technique is used toindicate whether a 40 MHz RU has MU-MIMO (applicable to PPDUs with 40MHz or larger bandwidth). As an example, the MUSU subfield would havelength 1, 2, and 3 bits respectively for 40 MHz (MUSU=b0), 80 MHz(MUSU=b0,b1) and 160 MHz (MUSU=b0, . . . , b3), where each bit indicateswhether the corresponding 40 MHz RU has MU-MIMO PSDUs (MU-MIMOassignments) or SU PSDUs. In another embodiment, additional bits areadded to MUSU subfield such that it would indicate whether each bitindicates a 20 MHz RU or a 40 MHz RU. For instance, one bit (such as aprefix bit p0) would indicate whether the MU-MIMO RUs is 20 MHz or 40MHz where p0=0 indicates the RUs are 20 Mhz hence the MUSU isinterpreted as above, and p0=1 indicates the RUs are 40 Mhz hence theMUSU would have length 1, 2 and 4 and as 40 MHz (MUSU=p0, b0), 80 MHz(MUSU=p0, b0, b1), 160 MHz (MUSU=p0, b0, . . . , b3). In anotherinstance, two bits (such as prefix bits p0,p1) would indicate whetherthe MU-MIMO RUs is 20 MHz (p0,p1=00), 40 MHz (p0,p1=01), or 80 MHz(p0,p1=10).

The fields and subfields described in the above embodiments appear as aTXVECTOR parameter between MAC and PHY sub-layers in a transmitting STA(see FIG. 2). The fields and subfields described in the aboveembodiments appear as a RXVECTOR parameter between MAC and PHYsub-layers in a receiving STA (see FIG. 2). Specifically, the “MorePSDU” field described above would be a TXVECTOR parameter that isoptionally present for each sub-band that has multiple PSDUs in asub-band as shown in the example of FIG. 7. When “More PSDU” field isequal to one for a sub-band, the PHY sub-layer of the transmitting STAadds HE STF and/or HE LTF symbols before the subsequent PSDU asdescribed above.

The capability to aggregate multiple PSDUs in a single sub-band may belimited to some AP or STAs, hence some capability fields are describedbelow to indicate such capability. In HE Capabilities, a subfielddenoted by TXMultiPSDUCapability (1 bit) indicates whether an AP iscapable of aggregating multiple PSDUs in a single sub-band (similar tothe example in FIG. 7). If an AP is capable of aggregating multiplePSDUs in a single sub-band it sets TXMultiPSDUCapability=1, otherwise itsets it to TXMultiPSDUCapability=0. In another embodiment,TXMultiPSDUCapability may have multiple bits, e.g.,TXMultiPSDUCapability (2 bits) where it is encoded as follows: If an APis not capable of aggregating multiple PSDUs in a single sub-band itsets TXMultiPSDUCapability=0, and if it is capable of aggregating up totwo PSDUs in a single sub-band it sets TXMultiPSDUCapability=1, and ifit is capable of aggregating up to three PSDUs in a single sub-band itsets TXMultiPSDUCapability=2, and if it is capable of aggregating up tofour PSDUs in a single sub-band it sets TXMultiPSDUCapability=3.

In HE Capabilities, a subfield denoted by RXMultiPSDUCapability (1 bit)indicates whether a STA is capable of aggregating multiple PSDUs in asingle sub-band (similar to the example in FIG. 7). If a STA is capableof receiving multiple aggregated PSDUs in a single sub-band it setsRXMultiPSDUCapability=1, otherwise it sets it toRXMultiPSDUCapability=0. In another embodiment, RXMultiPSDUCapabilitymay have multiple bits, e.g., RXMultiPSDUCapability (2 bits), where itis encoded as follows: If a STA is not capable of aggregating multiplePSDUs in a single sub-band it sets RXMultiPSDUCapability=0, and if it iscapable of receiving up to two aggregated PSDUs in a single sub-band, itsets RXMultiPSDUCapability=1, and if it is capable of receiving up tothree aggregated PSDUs in a single sub-band, it setsRXMultiPSDUCapability=2, and if it is capable of receiving up to fouraggregated PSDUs in a single sub-band, it sets TXMultiPSDUCapability=3.

The capability to support DL MU MIMO in an OFDMA sub-band may be limitedto some AP or STAs, hence some capability fields are described below toindicate such capability. In HE Capabilities, a subfield denoted byTXMUOFDMACapability (1 bit) indicates whether an AP is capable ofsupport DL MU MIMO in an OFDMA sub-band (similar to the example in FIG.11). If an AP is capable of supporting DL MU MIMO in an OFDMA sub-band,it sets TXMUOFDMACapability=1, otherwise it sets it toTXMUOFDMACapability=0. If TXMUOFDMACapability=1, other capabilities ofDL MU MIMO transmission within HE Capabilities or VHT Capabilitiesapplies. In HE Capabilities, a subfield denoted by RXMUOFDMACapability(1 bit) indicates whether a STA is capable of receiving DL MU MIMO in anOFDMA sub-band (similar to the example in FIG. 11). If a STA is capableof receiving DL MU MIMO in an OFDMA sub-band it setsRXMUOFDMACapability=1, otherwise it sets it to RXMUOFDMACapability=0. IfRXMUOFDMACapability=1, other capabilities of DL MU MIMO reception withinHE Capabilities or VHT Capabilities applies.

Referring back to FIG. 5, since there are different payloads in an IEEE802.11ax/HE DL OFDMA (as in FIG. 5), they would have different lengthsand both MAC padding and PHY padding may be necessary. This indicatesthat the actual length of each payload would be different. In order tooffer power-saving advantages to the recipient of each payload, it maybe best if the actual length of each payload is indicated so that therecipient, knowing the actual length, stops decoding and processing thepadded parts.

Note that there may be more than four payloads multiplexed into a singleOFDMA PPDU (unlike the example shown in FIG. 5). Hence, all the lengthvalues (per each payload) need to be explicitly carried. Note that theselength values may be carried in either HE SIG-A or HE SIG-B symbols(e.g., 503, 504). In the following several methods for encoding all thelengths are described.

The first solution is to use differential coding to carry the length ofeach payload. First, the length indication would be in units of U bytes,e.g., U=4 bytes. A reference length is indicated for the longest payloador longest PSDU in absolute value and denote it by L0. L0 may have 16bits. Note that L0 may be the length for the primary access category(AC) that has won the contention. Next for all other payloads, adifferential method may be used to indicate their length. To do so,first denote the length for a shorter payload by Lx, and then the valueof Dx=L0-Lx is carried is indicated in HE SIG-AB. Since Dx is thedifference between two payload lengths, and since it is expected thatthe AP is not multiplexing payloads with significantly different length,it is expected that Dx requires a smaller number of bits, e.g., 7 bits.Note that the max value for Dx (e.g., 128 if 7 bits is used to representDx), limits the MAC scheduler to multiplex the payloads whose size haveat most 64×U=512 bytes difference. If 8 bits are assigned for Dx, thenthe max payloads difference would be 1024 bytes. This type ofdifferential encoding requires 16+7×(nSTA−1) bits, e.g., if nSTA=4 itwould require 37 bits.

Note that L_LENGTH (that is obtained from the L-SIG symbol as shown inthe example of FIG. 5) is used to calculate total number of symbols forlongest payload (Nsym). Then the reception time is calculated viaRXTIME=4×((L_LENGTH+3)/3)+20 and finallyNsym=floor((RXTIME-Legacy_Header-HE_Header)/Tsym), where Legacy_Headeris the total time duration of the legacy header (20 us) and HE_Header isthe total time duration of the HE PHY header.

FIG. 13A illustrates a schematic diagram of an example of differentialencoding for length indication. FIG. 13A shows a given payload 1300which has been padded by Null-MPDUs (which are null MAC protocol dataunits) so that its length becomes about the same as the longest payload.The actual length of this payload is Nsym(s) (e.g., 1305). However, thelength that is indicated in L-SIG is Nsym (which is the length of thelongest payload). In the example shown in FIG. 13A, Ds=1 OFDM symbol(e.g., 1301, 1302, 1303), since Nsym (e.g., 1304) has the value of 3while Nsym(s) (e.g., 1305) has the value of 2.

In FIG. 13A, which illustrates a second solution, differential encodingis used to encode the OFDM-symbol index. In this method, the length ofthe longest PSDU is obtained via L-SIG as described above. However, foreach payload there would be a Dx, where unlike the first method (seeFIG. 5), the value of Dx is reported as the difference in OFDM symbolsfor each payload. For instance, assume that the duration in number ofOFDM symbols that is obtained from L-SIG as described above is denotedby Nsym (e.g., 1304), and then assume the actual length of this payloadwithout any MAC padding (e.g., excluding the null PDUs) is Nsym(s)(e.g., 1305). Then in this solution, the difference between Nsym andNsym(s), denoted by Ds=Nsym-Nsym(s), is encoded and carried in the HESIG AB of the DL OFDMA PPDU. Note that Nsym(s) is the number of OFDMsymbols (e.g., 1301, 1302) for a given payload, excluding any overflowof a null MPDU to the next symbol (e.g., 1303) as shown in FIG. 13A.

FIG. 13B illustrates a schematic diagram of another example ofdifferential encoding for length indication. This third solution isbased on differential encoding method for both length (in bytes) andduration (in number of OFDM symbols). FIG. 13B shows a given payload,which has been padded by Null-MPDUs so that its length becomes about thesame as the longest payload. The actual length of this payload isNsym(s) (e.g., 1355). However, the length that is indicated in L-SIG isNsym (which is the length of the longest payload) (e.g., 1354). Inaddition to the value of Ds, the value of the Dz (e.g., 1356) isreported which is the total number of bytes (in units of U bytes) thatare the padded values in the last OFDM symbol (whose content is notentirely null MPDUs) (e.g., 1352). In the example shown in FIG. 13B,Ds=1 OFDM symbol, since Nsym has the value of 3 while Nsym(s) has thevalue of 2, and Dz (e.g., 1356) has the length of a null MPDU (in unitsof U bytes).

The value of L0 as described in the first solution above is carried inthe HE SIG-B of the DL OFDMA PPDU. Then the value of L_LENGTH from L-SIGsymbol is used to calculate Nsym (e.g., 1354). Then for each payload (oreach PSDU), two differential lengths are reported. First differentialnumber of OFDM symbols as described in the second solution above(Ds=Nsym−Nsym(s)) is reported. Then the number of the padded bytes inthe last OFDM symbol (e.g., 1352) (whose content is not entirely nullMPDU) in units of U is reported, this value is denoted by Dz (e.g.,1356). Note that Dz may be rounded down in case byte boundaries (inunits of U bytes) does not coincide with OFDM symbol boundary. Note thatthis method is good if AP MAC scheduler multiplexes payloads with largelength differences. Compared to the second method (see FIG. 13A), thismethod allows the receiver to shut off the PHY processing at thebeginning of MAC padding, while in the second method some of the MACpadding that happen to be in the last OFDM symbol (that is not entirelyconsists of Null MPDUs) may still be decoded by the receiver. The numberof bits to represent Ds is small e.g., 1-3 bits. However, the receivermay still decode a few null MPDUs, but would avoid decoding OFDM symbolswhose content (for the given recipient) is entirely null MPDUs (e.g.,1353).

The fields and subfields described in the above embodiments appear as aTXVECTOR parameter between MAC and PHY sub-layers in a transmitting STA(e.g., see FIG. 2). The fields and subfields described in aboveembodiments appear as a RXVECTOR parameter between MAC and PHYsub-layers in a receiving STA (e.g., see FIG. 2). Specifically, thelength values described above, either as absolute values or asdifferential values represented in units of several bytes or units ofOFDM symbols, would be a TXVECTOR parameter that is present for eachsub-band.

For the first solution described above (e.g., see FIG. 5), the length L0for one payload (which is the payload that has the largest length) andthe differential length Dx for all other sub-bands are present asTXVECTOR parameters. In one embodiment, these values are represented bythe array (L0, Dx1, Dx2, . . . ) for all the payloads that the APdecides to fit in a DL OFDMA PPDU, where the number of bits used torepresent L0 is e.g., 16 bits and the number of bits used to representDs value is e.g., 6 bits. The L0, Dx1, Dx2, TXVECTOR parameters areplaced in the fields of HE SIG-A or HE SIG-B where the number of bitsfor L0 is e.g., 16 bits and the number of bits used to represent Dsvalue is e.g., 6 bits. In a STA that is a recipient of one the payloadsin a DL OFDMA PPDU, the STA first finds out which of the payloads belongto the STA (by using AID or PAID values that are associated to eachpayload) and then it passes L0 and the appropriate Ds values as RXVECTORparameters to the MAC layer (e.g., 211 of FIG. 2). Then MAC layercalculates the actual length of the payload that belongs to the STA andnotifies PHY (e.g., 215 of FIG. 2) to process the received payload up tothe length that is denoted by L0-Dx (in units of U bytes).

For the second solution described above (e.g., see FIG. 13A), the totalnumber of payload symbols in the received DL OFDMA PPDU, Nsym, and thedifferential length Ds for all sub-bands are present as TXVECTORparameters. In one embodiment, these values are represented by the array(Ds1, Ds2, . . . ) for all the payloads that the AP decides to fit in aDL OFDM PPDU, where the number of bits used to represent Ds values ise.g., 6 bits. The Ds1, Ds2, . . . TXVECTOR parameters are placed in thefields of HE SIG-A or HE SIG-B where the number of bits for each Dsvalue is e.g., 6 bits. In a STA that is recipient of one the payloads ina DL OFDMA PPDU, the STA first finds out which of the payloads belong tothe STA (by using AID or PAID values that are associated to eachpayload) and then it the appropriate Ds value as RXVECTOR parameters tothe MAC layer. Then MAC layer calculates the actual length of thepayload that belongs to the STA and notifies PHY to process the receivedpayload up to the OFDM symbol that is denoted by Nsym-Ds.

For the third solution described above (e.g., see FIG. 13B), the lengthL0 for one sub-band (which is the payload that has the largest length)and the total number of payload symbols in the received DL OFDMA PPDU,Nsym, and the differential lengths Ds and Dz for all sub-bands arepresent as TXVECTOR parameters. In one embodiment, these values arerepresented by the array (L0, Ds1, Ds2, Dz1, Dz2, . . . ) for all thepayloads that the AP decides to fit in a DL OFDMA PPDU, where the numberof bits used to represent Ds values is e.g., 6 bits. The Ds1, Ds2, . . ., Dz1, Dz2, . . . TXVECTOR parameters are placed in the fields of HESIG-A or HE SIG-B where the number of bits for each Ds value is e.g., 6bits. In a STA that is recipient of one the payloads in a DL OFDMA PPDU,the STA first finds out which of the payloads belong to the STA (byusing AID or PAID values that are associated to each payload) and thenthe appropriate Dz value as RXVECTOR parameters to the MAC layer. ThenMAC layer calculates the actual length of the payload that belongs tothe STA and notifies PHY to process the received payload up to the OFDMsymbol that is denoted by Nsym-Ds and to ignore the last L0-Dz bytes.

FIGS. 14A-14C illustrate flow charts of examples of aggregation methodsfor DL OFDMA operation. For explanatory and illustration purposes, theexample processes 1410, 1420 and 1430 may be performed by the wirelesscommunication devices 111-115 of FIG. 1 and their components such as abaseband processor 210, a MAC processor 211, a MAC software processingunit 212, a MAC hardware processing unit 213, a PHY processor 215, atransmitting signal processing unit 280 and/or a receiving signalprocessing unit 290; however, the example processes 1410, 1420 and 1430are not limited to the wireless communication devices 111-115 of FIG. 1or their components, and the example processes 1410, 1420 and 1430 maybe performed by some of the devices shown in FIG. 1, or other devices orcomponents. Further for explanatory and illustration purposes, theblocks of the example processes 1410, 1420 and 1430 are described hereinas occurring in serial or linearly. However, multiple blocks of theexample processes 1410, 1420 and 1430 may occur in parallel. Inaddition, the blocks of the example processes 1410, 1420 and 1430 neednot be performed in the order shown and/or one or more of theblocks/actions of the example processes 1410, 1420 and 1430 need not beperformed. Various examples of aspects of the disclosure are describedbelow as clauses for convenience. These are provided as examples, and donot limit the subject technology. As an example, some of the clausesdescribed below are illustrated in FIGS. 14A through 14C.

The embodiments provided herein have been described with reference to awireless LAN system; however, it should be understood that thesesolutions are also applicable to other network environments, such ascellular telecommunication networks, wired networks, etc.

An embodiment of the present disclosure may be an article of manufacturein which a non-transitory machine-readable medium (such asmicroelectronic memory) has stored thereon instructions which programone or more data processing components (generically referred to here asa “processor” or “processing unit”) to perform the operations describedherein. In other embodiments, some of these operations may be performedby specific hardware components that contain hardwired logic (e.g.,dedicated digital filter blocks and state machines). Those operationsmay alternatively be performed by any combination of programmed dataprocessing components and fixed hardwired circuit components.

In some cases, an embodiment of the present disclosure may be anapparatus (e.g., an AP STA, a non-AP STA, or another network orcomputing device) that includes one or more hardware and software logicstructure for performing one or more of the operations described herein.For example, as described above, the apparatus may include a memoryunit, which stores instructions that may be executed by a hardwareprocessor installed in the apparatus. The apparatus may also include oneor more other hardware or software elements, including a networkinterface, a display device, etc.

Clause A. A station for facilitating multi-user communication in awireless network, the station comprising: one or more memories; and oneor more processors coupled to the one or more memories, the one or moreprocessors configured to cause: receiving a downlink frame, the downlinkframe comprising a first signaling field and a second signaling field;determining whether the first signaling field indicates a multi-user(MU)-multi-input multi-output (MIMO) transmission in the downlink frame;when the first signaling field indicates the MU-MIMO transmission,determining one or more attributes of the MU-MIMO transmission in thesecond signaling field; when the first signaling field indicates atransmission that is a non-MU-MIMO transmission, determining one or moreattributes of the non-MU-MIMO transmission in the second signalingfield; decoding one or more portions of the downlink frame based on theone or more attributes of the MU-MIMO transmission or the one or moreattributes of the non-MU-MIMO transmission; and providing the decodedone or more portions of the downlink frame for processing.

Clause B. A non-transitory computer-readable storage medium storingcomputer-executable instructions that, when executed by one or moreprocessors, cause one or more processors to perform operations, theoperations comprising: generating a downlink frame for a multi-usertransmission, the downlink frame comprising a first signaling field anda second signaling field, wherein the first signaling field indicateswhether the downlink frame is associated with a multi-user(MU)-multi-input multi-output (MIMO) transmission, wherein the secondsignaling field comprises one or more attributes of the MU-MIMOtransmission when the downlink frame is associated with the MU-MIMOtransmission, wherein the second signaling field comprises one or moreattributes of a non-MU-MIMO transmission when the downlink frame isassociated with the non-MU-MIMO transmission; and providing the downlinkframe for the multi-user transmission directed to a plurality ofstations.

Clause C. A computer-implemented method of facilitating multi-usercommunication in a wireless network, the method comprising: receiving adownlink frame, the downlink frame comprising a first signaling fieldand a second signaling field; determining whether the first signalingfield indicates a multi-user (MU)-multi-input multi-output (MIMO)transmission in the downlink frame; when the first signaling fieldindicates the MU-MIMO transmission, determining one or more attributesof the MU-MIMO transmission in the second signaling field; decoding oneor more portions of the downlink frame based on the one or moreattributes of the MU-MIMO transmission; and providing the decoded one ormore portions of the downlink frame for processing.

In one or more aspects, additional clauses are described below.

A method comprising one or more methods or operations described herein.

An apparatus comprising one or more memories (e.g., 240, one or moreinternal, external or remote memories, or one or more registers) and oneor more processors (e.g., 210) coupled to the one or more memories, theone or more processors configured to cause the apparatus to perform oneor more methods or operations described herein.

An apparatus comprising means (e.g., 210) adapted for performing one ormore methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) comprisinginstructions stored therein, the instructions comprising code forperforming one or more methods or operations described herein.

In one aspect, a method may be an operation, an instruction, or afunction and vice versa. In one aspect, a clause may be amended toinclude some or all of the words (e.g., instructions, operations,functions, or components) recited in other one or more clauses, one ormore sentences, one or more phrases, one or more paragraphs, and/or oneor more claims.

To illustrate the interchangeability of hardware and software, itemssuch as the various illustrative blocks, modules, components, methods,operations, instructions, and algorithms have been described generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application.

A reference to an element in the singular is not intended to mean oneand only one unless specifically so stated, but rather one or more. Forexample, “a” module may refer to one or more modules. An elementproceeded by “a,” “an,” “the,” or “said” does not, without furtherconstraints, preclude the existence of additional same elements.

Headings and subheadings, if any, are used for convenience only and donot limit the invention. The word exemplary is used to mean serving asan example or illustration. To the extent that the term include, have,or the like is used, such term is intended to be inclusive in a mannersimilar to the term comprise as comprise is interpreted when employed asa transitional word in a claim. Relational terms such as first andsecond and the like may be used to distinguish one entity or action fromanother without necessarily requiring or implying any actual suchrelationship or order between such entities or actions.

Phrases such as an aspect, the aspect, another aspect, some aspects, oneor more aspects, an implementation, the implementation, anotherimplementation, some implementations, one or more implementations, anembodiment, the embodiment, another embodiment, some embodiments, one ormore embodiments, a configuration, the configuration, anotherconfiguration, some configurations, one or more configurations, thesubject technology, the disclosure, the present disclosure, othervariations thereof and alike are for convenience and do not imply that adisclosure relating to such phrase(s) is essential to the subjecttechnology or that such disclosure applies to all configurations of thesubject technology. A disclosure relating to such phrase(s) may apply toall configurations, or one or more configurations. A disclosure relatingto such phrase(s) may provide one or more examples. A phrase such as anaspect or some aspects may refer to one or more aspects and vice versa,and this applies similarly to other foregoing phrases.

A phrase “at least one of” preceding a series of items, with the terms“and” or “or” to separate any of the items, modifies the list as awhole, rather than each member of the list. The phrase “at least one of”does not require selection of at least one item; rather, the phraseallows a meaning that includes at least one of any one of the items,and/or at least one of any combination of the items, and/or at least oneof each of the items. By way of example, each of the phrases “at leastone of A, B, and C” or “at least one of A, B, or C” refers to only A,only B, or only C; any combination of A, B, and C; and/or at least oneof each of A, B, and C.

It is understood that the specific order or hierarchy of steps,operations, or processes disclosed is an illustration of exemplaryapproaches. Unless explicitly stated otherwise, it is understood thatthe specific order or hierarchy of steps, operations, or processes maybe performed in different order. Some of the steps, operations, orprocesses may be performed simultaneously. The accompanying methodclaims, if any, present elements of the various steps, operations orprocesses in a sample order, and are not meant to be limited to thespecific order or hierarchy presented. These may be performed in serial,linearly, in parallel or in different order. It should be understoodthat the described instructions, operations, and systems can generallybe integrated together in a single software/hardware product or packagedinto multiple software/hardware products.

The disclosure is provided to enable any person skilled in the art topractice the various aspects described herein. In some instances,well-known structures and components are shown in block diagram form inorder to avoid obscuring the concepts of the subject technology. Thedisclosure provides various examples of the subject technology, and thesubject technology is not limited to these examples. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the principles described herein may be applied to otheraspects.

All structural and functional equivalents to the elements of the variousaspects described throughout the disclosure that are known or later cometo be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. § 112, sixth paragraph, unless theelement is expressly recited using a phrase means for or, in the case ofa method claim, the element is recited using the phrase step for.

The title, background, brief description of the drawings, abstract, anddrawings are hereby incorporated into the disclosure and are provided asillustrative examples of the disclosure, not as restrictivedescriptions. It is submitted with the understanding that they will notbe used to limit the scope or meaning of the claims. In addition, in thedetailed description, it can be seen that the description providesillustrative examples and the various features are grouped together invarious implementations for the purpose of streamlining the disclosure.The method of disclosure is not to be interpreted as reflecting anintention that the claimed subject matter requires more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed configuration or operation. The following claims arehereby incorporated into the detailed description, with each claimstanding on its own as a separately claimed subject matter.

The claims are not intended to be limited to the aspects describedherein, but are to be accorded the full scope consistent with thelanguage claims and to encompass all legal equivalents. Notwithstanding,none of the claims are intended to embrace subject matter that fails tosatisfy the requirements of the applicable patent law, nor should theybe interpreted in such a way.

1-20. (canceled)
 21. A wireless device, comprising: a processing device;and a memory unit coupled to the processing device, wherein the memoryunit includes instructions that when executed by the processing devicecause the wireless device to: set a more data field in a frame to betransmitted to a set of stations in a wireless network, wherein the moredata field indicates whether a first set of training fields are presentin the frame, add the first set of training fields to the frame when themore data field is set to a predetermined value, and transmit the frameto the set of stations.
 22. The wireless device of claim 21, wherein theinstructions, when executed by the processing device, further cause thewireless device to: add a first set of data fields to the frame; andadd, when the more data field is set to the predetermined value, asecond set of data fields to the frame following the first set of datafields.
 23. The wireless device of claim 22, wherein the first set oftraining fields are located between the first set of data fields and thesecond set of data fields.
 24. The wireless device of claim 23, whereinthe first set of training fields is a set of high efficiency longtraining fields that are to assist the set of stations perform physicallayer processing on the frame.
 25. The wireless device of claim 24,wherein the instructions, when executed by the processing device,further cause the wireless device to: add a second set of trainingfields to the frame, wherein the second set of training fields are theset of high efficiency long training fields.
 26. The wireless device ofclaim 25, wherein the second set of training fields are located in theframe before the first set of training fields.
 27. The wireless deviceof claim 26, wherein the first set of training fields, the first set ofdata fields, and the second set of data fields are located in a dataportion of the frame and the second set of training fields are locatedin a preamble of the frame.
 28. The wireless device of claim 26, whereina number of symbols for the first and second set of training fields isdependent on a number of spatial streams associated with a resource unitin which the first and second set of training fields are carried in theframe.
 29. The wireless device of claim 26, wherein the first set ofdata fields is a same length as the second set of data fields.
 30. Thewireless device of claim 21, wherein the more data field consists of asingle bit and the predetermined value is the value one.
 31. Thewireless device of claim 21, wherein the instructions, when executed bythe processing device, further cause the wireless device to: set a firstsignaling field of the frame to indicate whether the frame is part of amulti-user (MU)-multi-input multi-output (MIMO) transmission; when thefirst signaling field is set to indicate the MU-MIMO transmission,setting one or more attributes of the MU-MIMO transmission in a secondsignaling field of the frame; and when the first signaling field is setto indicate a transmission that is a non-MU-MIMO transmission, set oneor more attributes of the non-MU-MIMO transmission in the secondsignaling field.
 32. A wireless device, comprising: a processing device;and a memory unit coupled to the processing device, wherein the memoryunit includes instructions that when executed by the processing devicecause the wireless device to: process a more data field in a framereceived from a station in a wireless network, wherein the more datafield indicates whether a first set of training fields are present inthe frame, process a first set of data fields in the frame, process thefirst set of training fields in the frame when the more data field isset to a predetermined value, and process a second set of data fields inthe frame when the more data field is set to the predetermined value.33. The wireless device of claim 32, wherein the first set of trainingfields are located between the first set of data fields and the secondset of data fields.
 34. The wireless device of claim 33, wherein thefirst set of training fields is a set of high efficiency long trainingfields that are to assist the wireless device perform physical layerprocessing on the frame.
 35. The wireless device of claim 34, whereinthe instructions, when executed by the processing device, further causethe wireless device to: process a second set of training fields in theframe, wherein the second set of training fields are located in theframe before the first set of training fields and, wherein the secondset of training fields are the set of high efficiency long trainingfields.
 36. The wireless device of claim 35, wherein the first set oftraining fields, the first set of data fields, and the second set ofdata fields are located in a data portion of the frame and the secondset of training fields are located in a preamble of the frame.
 37. Thewireless device of claim 35, wherein a number of symbols for the firstand second set of training fields is dependent on a number of spatialstreams associated with a resource unit in which the first and secondset of training fields are carried in the frame.
 38. The wireless deviceof claim 35, wherein the first set of data fields is a same length asthe second set of data fields.
 39. The wireless device of claim 32,wherein the more data field consists of a single bit and thepredetermined value is the value one.
 40. The wireless device of claim32, wherein the instructions, when executed by the processing device,further cause the wireless device to: determine whether a first headerfield of the frame indicates a first type of transmission or a secondtype of transmission; determine one or more attributes of the first typeof transmission in a second header field of the frame when the firstheader field is determined to indicate the first type of transmission;determine one or more attributes of the second type of transmission inthe second header field of the frame when the first header field isdetermined to indicate the second type of transmission; and process oneor more portions of the frame based on the one or more attributes of thefirst type of transmission or the one or more attributes of the secondtype of transmission.